1. Field of the Invention
The present invention relates to driving a step motor. More particularly, the present invention relates to driving a step motor in a low power consumption mode.
2. Description of the Related Art
Step motors may be used in paper outputting devices, such as printers or facsimiles, heads of floppy disks, optical disk devices, micro-mouses, industrial robot arms, etc., since they can accurately control speeds or locations.
Information on current location and movement location of an object may be used to drive step motors. This information may include coordinate values of the current and movement locations of the object. Step motors may use two control signals when the object moves in a 2-dimensional space.
FIG. 1 is a graph illustrating two signals driving a step motor. Referring to FIG. 1, two coordinate values may be used to drive the step motor. The two coordinate values may correspond to points where a sine wave and a cosine wave overlap. A first coordinate value may be used to move an object. The first coordinate value may be a point on the sine wave. The second coordinate value may be a point on the cosine wave corresponding to the first coordinate. For example, two pairs of coordinate information P1 and P2, and P3 and P4, respectively, may be used to drive the step motor. The step motor may detect differences between a current location and a movement location of an object which allows the object to arrive at a final destination using the detected information.
The difference information may be considered error information. When the error signal falls within a predetermined offset, a system stops supplying power to a circuit driving the step motor during a predetermined period of time so as to reduce power consumption. For example, when a system reads information stored on an optical disk, a lens may perform tracking along the optical disk storing the information. In this regard, an excessive action of a servo is not required, i.e., the tracking operation falls within the predetermined offset, according to the status of the optical disk or an optical disk apparatus. Thus, supplying power to the circuit driving the step motor under these circumstances may result in unnecessary power consumption.
FIG. 2 is a graph illustrating two signals driving the step motor to reduce power consumption. Referring to FIG. 2, a bold-lined signal may be used in a normal state, and a thin-lined pulse signal may be used to reduce power consumption. The sine wave illustrated in FIG. 2 will now be described in relation to FIG. 1. The thin-lined pulse signal may include a pulse train based on a reference voltage Vref. The reference voltage Vref has a DC value. The period of time where the thin-lined pulse signal meets the bold-lined signal indicates the size or amplitude of a pulse. Accordingly, the maximum and minimum values of the pulse is VP(+) and VP(−). Thus, the thin-lined pulse signal may rapidly vary according to differences between the reference voltage Vref and the bold-lined signal. The voltage variation of the thin-lined pulse signal is {VP(+)−Vref} or {Vref−VP(−)}. However, this voltage variation may deteriorate the operation of the step motor and negatively affect peripheral circuits.